Trailer tongue jacks are employed to raise and lower a trailer tongue, such as a boat trailer tongue, to facilitate hitching of the trailer to a vehicle. The typical tongue trailer jack also includes a supporting caster wheel so that when the trailer is unhitched from the vehicle, the jack will support the tongue, and the caster wheel will facilitate movement of the trailer over the ground. In some instances a sand shoe may be used in place of the caster wheel to support the trailer tongue on soft terrain.
The conventional jack construction includes an outer elongated tube and an inner tube which is mounted for telescopic sliding movement within the outer tube. The lower end of the inner tube is connected through a swivel to a caster wheel or sand shoe.
To move the inner tube and caster wheel or sand shoe relative to the outer tube, a nut is secured within the upper end of the inner tube and is engaged with an elongated screw. In a common type of jack, the upper end of the screw extends through an opening in a U-shaped bracket that is mounted within the upper end of the outer tube and a bevel gear is secured to the end of the screw. The bevel gear meshes with a second bevel gear located with the U-shaped bracket and the second bevel gear is driven by rotation of a manually operated handle. With this construction, rotation of the handle will operate through the bevel gears to rotate the screw and thereby move the nut and inner tube up and down relative to the outer tube. As the outer tube is connected to the trailer tongue, lowering of the inner tube and caster wheel relative to the outer tube will lift the trailer tongue, and conversely, upward movement of the inner tube and caster wheel relative to the outer tube will lower the trailer tongue.
The typical drive mechanism for the jack as used in the past has required a number of separate components. More specifically, bushings are utilized to journal the handle in both flanges of the U-shaped bracket and an additional bushing is required to journal the screw relative to the bottom surface or web of the bracket. Further, the typical construction as used in the past has included a thrust bearing mounted on the upper end of the nut in position to engage the bottom surface of the bracket.
In addition, the conventional construction has employed retaining pins to retain the handle within the bracket and also to retain the bevel gears on the screw and handle. The use of the bushings, thrust bearing and pins contributed substantially to the overall cost of the jack.
The typical trailer tongue jack also includes a provision for pivoting the jack, once the trailer is hitched and the caster wheel is elevated out of contact with the ground, to a generally horizontal storage position so that the jack will not interfere with travel of the vehicle or trailer. The typical mechanism for providing this pivoting action has consisted of a swivel bracket which is secured to the outer surface of the outer tube of the jack and a mounting plate, which is attached to the trailer tongue and is connected to the swivel bracket through a pivot. The jack can be locked in either a vertical or horizontal position by a spring loaded locking pin that is mounted on the swivel bracket and is engageable within a hole in the mounting plate on the tongue. To pivot the jack, two handed operation is required, with one hand releasing the spring loaded locking pin and the other hand then pivoting the jack to the horizontal storage position.